Dual frequency window mount antenna

Apparatus for transmitting signals between a telephone lying on an inner side of a dielectric plate such as a window, and an antenna on the outer side of the dielectric plate, which is efficient at a lower cell phone band of about 850 MHz where a quarter wavelength is about 3.6 inches and that is also efficient at an upper cell phone band of about 1920 MHz where a quarter wavelength is about 1.6 inches, comprising:

• a metal box device lying on said inner side of said dielectric plate, said box device having a bottom wall lying furthest from said dielectric plate and having side walls extending from a periphery of said bottom wall in an outer direction towards said dielectric plate, with a side of said box device opposite said bottom wall being open;
• an inner conductive plate of electrically conductive material lying in said open side of said box device opposite said bottom wall, said inner conductive plate having an inner face facing said bottom wall but being out of electrical contact with said box, said inner conductive plate having an outer face lying facewise adjacent to an inner face of said dielectric plate;
• an outer conductive plate device of conductive material that includes an outer plate part lying facewise adjacent to an outer face of said dielectric plate and connected to said antenna;
• a coaxial cable which has a ground conductor connected to said box device and a signal conductor connected to said conductive inner plate;
• said inner conductive plate having a plurality of corners and having a plurality of sides extending between said corners;
• said conductive inner plate is of substantially rectangular shape, with a pair of first opposite sides each of a first length and a pair of second opposite sides each of a second length, and said signal conductor is connected to the middle of one of said sides;
• the distance between the middle of one of said sides plus the length of an adjacent other side of said inner conductive plates, is about equal to 1.6 inches, while the circumference of said inner conductive plate is about equal to 3.6 inches.